Field of the Invention
The invention relates to the management of the mass of fuel injected into engines, in particular during their starting phase. In a main, although not exclusive application, the invention relates to the internal combustion engines of motor vehicles utilizing different fuels, for example: petrol, a petrol/ethanol mixture, diesel or other gases (LPG, etc.).
Description of the Related Art
The constituent elements of such engines regularly undergo modifications to take account of technical advances, for example electronic injection or the system of injection with a common rail (referred to as “common rail”), as well as the ongoing objectives of weight reduction, lower fuel consumption, fuel diversification and reduction of costs. Up to now, however, engines have exhibited high risks of non-starting at low temperature regardless of the fuel. Depending on the fuel that is utilized, it is essential that its temperature remains above a minimum value. This minimum value for guaranteeing starting is −30° C. in the case of petrol and −5° C. in the case of ethanol.
Numerous improvements have been made to internal combustion engines within the context of the steady speed operation of the engine, that is to say after the starting phase. One important aspect of the correct functioning of this steady speed operating condition is the quantity of combustion air and fuel that are injected into the combustion chamber, said quantity being expressed in terms of a mass. For example, patent document US 2008/0288159 describes an improvement in the combustion by controlling the mass of the components that are injected into the engine. Patent document FR 2 790 283 also discloses an improvement in the control of the pressure of the fuel. And patent document EP 0 725 212 presents an improvement to the system for the injection of fuel at high pressure.
In general, the starting phase is treated in the same manner as the steady speed operating condition of the engine. When running at a steady speed, the parameters that are taken into account in order to adapt the quantities of fuel or combustion air are many and varied, for example: the temperature of the water in the cylinder head, the rpm of the engine, the quality and the type of fuel utilized, the pressure and the temperature of the air in the inlet manifold. And these data are then applied for the management of the starting phase. The principal characterizing feature of the starting phase is the fact that the engine is stationary and cold, at the ambient temperature of the place where it is situated. Furthermore, the current proliferation of fuel types requires ambient temperatures to be taken into account in a wide range of values in order to obtain reliable starting of the engine, for example from as low as −5° C. in the case of pure ethanol.
Also familiar is document US 2012/0203444 A1, which relates to a starting control device applied to an engine injection system having a starter which drives the crankshaft, a fuel pump, a common rail which accumulates a high pressure of fuel delivered by the fuel pump, and an injector which injects the fuel under high pressure into the cylinder. The starting control device comprises a unit for the electronic control of the engine (ECU, stands for Engine Control Unit in English) which determines whether the conditions relating to the startability of the engine have decreased. If the ECU determines that the conditions relating to the startability of the engine have decreased, it reduces the quantity of fuel which passes from the rail towards the injector during one revolution of the crankshaft. In particular, the reduction in the quantity of fuel is increased when the pressure inside the common rail becomes lower than an optimum target pressure which is suitable for each operating state of the engine.